Seismic rehabilitation of masonry-infilled concrete frames by adding new cast-in-place reinforced concrete walls

The behavior of non-ductile concrete frames infilled with unreinforced masonry walls rehabilitated by adding a new cast-in-place reinforced concrete (RC) wall was assessed experimentally. Four large-scale identical one-bay and one-story RC frames infilled with a concrete-masonry-unit wall were constructed and rehabilitated by adding a new cast-in-place RC wall. The specimens were tested under a cyclic loading history that simulated earthquake-motions demands. Variables included the type of connectors used to fasten the new RC wall to the existing infilled frame, and the connectors layout. Epoxy-grouted steel deformed bars and powder-actuated fasteners were used. Results of the test program indicated that the rehabilitated specimens showed better strength, stiffness, and energy dissipation characteristics than the existing structure. Test data support that composite action could be realized if surface preparation and adequate layout and type of connectors are used. A light surface preparation of masonry and concrete surfaces, consistent with an average roughness of 0.4 mm, is recommended. Also, it was found that is preferable to design epoxy-grouted deformed bars using a capacity-design approach to avoid premature failure of the connection and to install them along the perimeter frame. Design of the rehabilitated structure can be done by assuming that lateral strength of the retrofitted structure be calculated by adding the shear strength contribution of the new RC wall and the strength of the existing masonry infill at crushing. The elastic uncracked stiffness can be estimated by assuming a wide-column model.